>TIGR01729 taurine_ABC_bnd taurine ABC transporter, periplasmic binding protein; InterPro: IPR010068 ABC transporters belong to the ATP-Binding Cassette (ABC) superfamily, which uses the hydrolysis of ATP to energize diverse biological systems. ABC transporters are minimally constituted of two conserved regions: a highly conserved ATP binding cassette (ABC) and a less conserved transmembrane domain (TMD). These regions can be found on the same protein or on two different ones. Most ABC transporters function as a dimer and therefore are constituted of four domains, two ABC modules and two TMDs. ABC transporters are involved in the export or import of a wide variety of substrates ranging from small ions to macromolecules. The major function of ABC import systems is to provide essential nutrients to bacteria. They are found only in prokaryotes and their four constitutive domains are usually encoded by independent polypeptides (two ABC proteins and two TMD proteins). Prokaryotic importers require additional extracytoplasmic binding proteins (one or more per systems) for function. In contrast, export systems are involved in the extrusion of noxious substances, the export of extracellular toxins and the targeting of membrane components. They are found in all living organisms and in general the TMD is fused to the ABC module in a variety of combinations. Some eukaryotic exporters encode the four domains on the same polypeptide chain . The ABC module (approximately two hundred amino acid residues) is known to bind and hydrolyze ATP, thereby coupling transport to ATP hydrolysis in a large number of biological processes. The cassette is duplicated in several subfamilies. Its primary sequence is highly conserved, displaying a typical phosphate-binding loop: Walker A, and a magnesium binding site: Walker B. Besides these two regions, three other conserved motifs are present in the ABC cassette: the switch region which contains a histidine loop, postulated to polarize the attaching water molecule for hydrolysis, the signature conserved motif (LSGGQ) specific to the ABC transporter, and the Q-motif (between Walker A and the signature), which interacts with the gamma phosphate through a water bond. The Walker A, Walker B, Q-loop and switch region form the nucleotide binding site , , . The 3D structure of a monomeric ABC module adopts a stubby L-shape with two distinct arms. ArmI (mainly beta-strand) contains Walker A and Walker B. The important residues for ATP hydrolysis and/or binding are located in the P-loop. The ATP-binding pocket is located at the extremity of armI. The perpendicular armII contains mostly the alpha helical subdomain with the signature motif. It only seems to be required for structural integrity of the ABC module. ArmII is in direct contact with the TMD. The hinge between armI and armII contains both the histidine loop and the Q-loop, making contact with the gamma phosphate of the ATP molecule. ATP hydrolysis leads to a conformational change that could facilitate ADP release. In the dimer the two ABC cassettes contact each other through hydrophobic interactions at the antiparallel beta-sheet of armI by a two-fold axis , , , , , . Proteins known to belong to this family are classified in several functional subfamilies depending on the substrate used (for further information see http://www.tcdb.org/tcdb/index.php?tc=3.A.1). This entry identifies a cluster of ABC transporter periplasmic substrate binding proteins, apparently specific for taurine. Transport systems for taurine (NH2-CH2-CH2-SO3H), sulphonates, and sulphate esters import sulphur when sulphate levels are low. The most closely related proteins outside this family are putative aliphatic sulphonate binding proteins..

Probab=98.78  E-value=2e-08  Score=74.58  Aligned_cols=221  Identities=15%  Similarity=0.159  Sum_probs=159.8

Q ss_pred             HHHCCCCEEEEEECCH-HHHHHHHHCCCCEEEEEEECCCCHHHHHHHHHCCCEEEE-CCCCCCCEEEEEEEHHHHHCCCC
Q ss_conf             9610698489985640-578888514981399984046413566665530470230-13566853567863446412345
Q gi|254780342|r   49 LEEILGYKTNIKLLAV-PVTFRSLKNKGIDIFMGYWYPSLEKFIAPYLEEGSIKLV-AENLQGAKYMLAVNDVGFALGIK  126 (309)
Q Consensus        49 LE~~lGy~Ve~~~~~~-~~~~~al~~G~iD~~~e~w~p~~~~~~~~~~~~~~~~~~-~~~~~~~~~~~~v~~~~~~~~i~  126 (309)
T Consensus        24 ~aKe~gaTiDWRkFdSGadi~~AlASG~V~IG~~GSsplaaAASr~v----pie~f~~~~~iG~SEALVar~g~---GIe   96 (304)
T TIGR01729        24 YAKEAGATIDWRKFDSGADIVAALASGDVDIGVVGSSPLAAAASREV----PIEVFLVVDKIGKSEALVAREGA---GIE   96 (304)
T ss_pred             HHHCCCCEEEEEEECCHHHHHHHHHCCCCCCCCCCCCHHHHHHHCCC----CEEEEEEECCCCCCCEEEEECCC---CCC
T ss_conf             54304880200110441655556533863322224707899872688----30020100102872002454367---887


Q ss_pred             CHHHHHHHHHHHHHCCCCCCCCCCCCHHHHHHHHH-CCCCCCCEEEECCCCCCHHHHHHHHHHCCCCEEEEEECCCHHHH
Q ss_conf             53565555665442013578543200555876640-35452210010366520189999999659936999412422320
Q gi|254780342|r  127 SYQDIAKYKKELGAKIYGIEPGNEGNQRILDMINN-NKFSLKGFRLIEASELASFSQIRRDQRNNIPAVFLSWEPHPINS  205 (309)
Q Consensus       127 ~~~dl~~~~~~~~~~~~g~~~~~~~~~~~~~~~~~-~~l~~~~~~~~~~s~~~~~a~l~~A~~~~~~~v~~~wsp~~~~~  205 (309)
T Consensus        97 KpeDL~-------GK~vaVPFvSTtHysLLaaLk~vw~~dp~~V~IlNl~PP----~I~AAwqRGDIDaAYVW~PAl~~l  165 (304)
T TIGR01729        97 KPEDLK-------GKKVAVPFVSTTHYSLLAALKHVWKVDPKEVEILNLKPP----EIVAAWQRGDIDAAYVWDPALSEL  165 (304)
T ss_pred             CHHHHC-------CCEEECCCCCHHHHHHHHHHHHHHCCCCCEEEEEECCCH----HHHHHHHCCCCCCCCCCHHHHHHH
T ss_conf             666717-------884502751134589999888762678760578617965----799875438826210374568877


Q ss_pred             CCCCEEECCCCCC--CCCCHHHHHHHHCHHHHHHCHHHHHHHHHC---------------CCCHHHHHHHHHHHHHCCCC
Q ss_conf             1585140078654--677865835442777787488999998740---------------89989999999999845999
Q gi|254780342|r  206 DLNIHYLPGGEEI--SGFGEASVYTVVRSDYLDKCPNISRLLKNI---------------KFSVALENEMMKLILNNKQD  268 (309)
Q Consensus       206 ~~dl~~Ledp~~~--~~~p~~~~~~vv~~~~~~~~P~~~~~L~~~---------------~ls~~~~~~l~~~v~~~g~~  268 (309)
T Consensus       166 ~k~GKV~~DSeqvgawgaPTfD-~wvvrkdfAeknPe~v~aF~Kv~~dAya~Y~Anpd~W~~~spq~~k~akL~---G~~  241 (304)
T TIGR01729       166 KKSGKVVSDSEQVGAWGAPTFD-AWVVRKDFAEKNPEVVKAFVKVLADAYADYLANPDAWKADSPQVSKLAKLI---GAD  241 (304)
T ss_pred             HHCCCEEECHHHHHHCCCCCCC-EEEEECHHHHHCHHHHHHHHHHHHHHHHHHCCCCCCCCCCCHHHCCEEEEE---CCC
T ss_conf             5359668525787413687310-246521454307078999998899850100238875667862112224440---688


Q ss_pred             HHHHHH-----HHHHHHHHHHHHHHCCC
Q ss_conf             899999-----99998599999875475
Q gi|254780342|r  269 RQFVGR-----TMLRTHPDLLKNWLIGV  291 (309)
Q Consensus       269 ~~~vA~-----~wL~~n~~~~~~Wl~~~  291 (309)
T Consensus       242 ~e~vp~llkg~~fpT~~eQ~sdk~lGGg  269 (304)
T TIGR01729       242 AEDVPELLKGLSFPTADEQVSDKLLGGG  269 (304)
T ss_pred             CCCHHHHHHCCCCCCHHHHHHHHHCCCC
T ss_conf             2313777622346785452002321673